Method and device for the disintegration of especially inorganic materials

ABSTRACT

The invention relates to a method for the disintegration and tribochemical activation of especially inorganic materials having a crystalline structure, wherein the starting materials are comminuted (disintegrated) to a particle size of less than 1 μm by the effect of impacting pressure fronts at a pulse duration of less that 10 μs and a sequence frequency of more than 8 kHz. A conglomerate of activated mixed crystals is then obtained. Said conglomerate has an increased aptitude for the formation of modified crystals when water is added. The duration of the effect of the impacting pressure fronts continues until the crystal lattice structure of the particles ( 30 ) is destroyed. A device for the disintegration and tribochemical activation of said materials is based on rotating disks whereon moulded bodies with aerodynamical profiles are arranged, said moulded bodies being continuously displaced in a transonic speed range and impacting pressure fronts being produced on the outflow surfaces thereof.

The invention relates to a method and an apparatus for thedisintegration and tribochemical activation in particular of inorganicmaterials.

Disintegrators are known for a number of applications. In cementproduction, for instance, on the industrial scale, chunks of limestoneand various additives are first comminuted, then heated to temperaturesof 1400° C. to 1600° C., sintered, and then ground to the desired grainsizes. The disadvantage of this method is that a large amount of energyis needed for activating the starting materials.

Known from DE 195 48 645 is attaining an elevated potential energycontent and thus increased chemical reactability using tribochemicallytreated crystals. For instance, mechanical activation of cementfacilitates a substantial increase in the strength of the hydratedmineral bonding agent. The reasons for this are the primary particlesize and the lattice distortions of these particles.

A plurality of processing methods are available for tribometricprocessing of starting materials such as e.g. grinding by stressingbetween two surfaces, or using collisions between freely mobileparticles and solid surfaces or collisions among the particlesthemselves. So-called disintegrators are used for inserting highpotential energy into the smallest of particles on a scale of a few 1 μmand for thus causing lattice distortions. The construction principle ischaracterized by two pin rings or ring gears. In one variant, asdescribed in DE-AS 12 36 915, the particles are comminuted in collisionswith pins or teeth. At least three collisions with pins at intervals ofno more than 50 ms at a relative speed of at least 15 m/s are requiredfor adequate activation. In this arrangement it is disadvantageous thatthe wear on the pins is very high, especially when using very hardstarting materials.

In another variant, e.g. in accordance with DE 30 34 849 A1, thestarting material is primarily comminuted using particle collisions invortices, the vortices being generated by specially shaped blade ringsdriven in opposite directions. At the same time wear is substantiallyreduced on the edges of the blade rings or ring gears that are impacted.

The activation that can be attained with known disintegrators or millsis not adequate for developing novel inorganic bonding agents.Particularly when there are small, light-weight particles such as occurafter brief milling, it is not possible to cause these particles tocollide at a high relative speed of for instance greater than 100 m/s byembedding these particles in a stream of air or in an air vortex.

The object of the invention is to provide a method and an apparatus fordisintegration in which dynamic treatment of the particles occurs withsubstantially increased energies and rates of effectiveness compared tothe prior art. This object of the invention is attained using adisintegrator of the generic type indicated in the foregoing in whichthe starting materials in the form of a granulate are subjected toimpact pressure waves from a broad frequency spectrum and a pulseduration of less than 10 μs. Further comminution of the particles,destroying the crystal lattice structure, occurs due to the effect ofthe impact pressure waves striking the particles in quick succession atsupersonic speed. As a result of this comminution, a conglomerate ofmixed crystals occurs that have an increased capacity for crystalformation when water is added later. The impact pressure waves aregenerated by shaped bodies with aerodynamically shaped profiles andsurfaces that are accelerated to the so-called transonic range. Withthese, impact pressure fronts are generated that pulverize the granulateintroduced into the disintegrator to the desired particle size. Theshaped bodies move on disks just below supersonic speed. Because of theeffect of high mechanical energy, in addition to being comminuted, theparticles are activated and thus undergo a change in chemicalproperties.

In the case of organic substances, pretreatment is required for thepurpose of reducing elasticity.

If the relative speed of the air flowing against the shaped bodies,including the particles suspended in the air, is now just below soundvelocity, the flow speed can in part reach supersonic speed relative tothe shaped body. The speed range below sound velocity at which the airflowing around the formed bodies in part has supersonic speed is calledthe transonic speed range in the literature (Sigloch: TechnischeFluidmechanik, VDI Publishing, 1996).

Appropriate protective gases can be employed instead of air for avoidingchemical reactions.

Depending on the shape of the aerodynamically shaped body, the transonicspeed range commences at 0.75 . . . 0.85 Mach and terminates when theshaped body attains sound velocity with regard to the air flowingagainst it.

If the speed of the air flowing against it relative to the shaped bodyis in the transonic speed range, supersonic speed relative to theaerodynamic profile of the shaped body occurs in a zone. This zone ofair flowing supersonically relative to the shaped body is limited by aforward front, a rear front, and the profile of the shaped body. Atransition from supersonic speed to normal speed takes place on the rearfront. This transition is accompanied by an impact pressure front, i.e.the air pressure rises to a multiple of normal pressure and then returnsto normal pressure after a brief low pressure phase. The specialcharacteristic of this impact pressure front is that the change inpressure is theoretically limited to a few molecule lengths, but inpractice it is on the magnitude of 100 μm due to heating and vortices,and in any case is very short with respect to the geometry of the shapedbodies.

These effects are adequately known in the development of support surfaceprofiles for supersonic aircraft and are undesired. The impact pressurefront severely stresses the exterior skin of the wings. In addition, thecompression of the air into an impact pressure front requires increasedpropulsion energy for the aircraft. There is therefore an attempt tomoderate the effects of the transonic speed range and to overcome thisrange rapidly (“break the sound barrier”) by specially designing thesupport surface profiles.

In accordance with the invention, the effects of the transonic speedrange are used for the comminution and activation of mineral granulate.The use of the impact pressure front is very efficient due to twofactors. First, the impact pressure front is a very brief pulse with abuild-up time of a few μs. Second, the immediate succession of pressureincrease and pressure decrease is very effective in terms ofmechanically stressing the granulate. In terms of spectrum, the pressureimpact can be understood as the sum of pressure waves of very differentfrequencies. Thus, depending on the steepness of the pressure impact,frequency portions of pressure waves with a few 100 kHz are alsoincluded. Therefore portions of a characteristic breaking frequency thatis particularly effective in the direction of the desired comminutionand activation occur for different particle sizes and consistency.

The inventive structure of the disintegrator thus subjects thegranulate, that is, the particles, to several hundred of these impactpressure fronts successively. This is initially attained by using aplurality of shaped bodies that rotate about a common axis. In addition,a counter-rotating group of shaped bodies prevents the relative speed ofthe shaped bodies from being reduced with respect to the air with theembedded granulate, that is, particles, due to pulling effects. Thus theparticles move relatively slowly, relative to sound velocity, throughthe disintegration space due to alternating pulling of the particles inthe one or other direction.

The repetition rate of the impact pressure fronts is in the supersonicrange, are inaudible, and can be dampened relatively well to protectoperators.

When the forward surfaces of the shaped body are designed suitably, theparticles seldom collide with the shaped bodies because in particularsmaller particles are pulled around the surface of the shaped bodies. Itis not necessary to provide special armoring or protection of theforward surfaces of the shaped bodies. It is only on the outlet side,that is, in the rear area relative to the flow, that higher loads occurat the point of intersection between the impact pressure front and thesurface of the shaped body, and these loads can be supported by suitablematerials such as high-alloy tool steels. It is useful to design thesurface of the shaped body as a so-called sub-critical profile, that is,the flow around it is largely laminar (Sigloch: TechnischeFluidmechanik; VDI Publishing, 1996). The shaped body is for instancerounded on the forward front and its off-flow surfaces meet at an acuteangle.

The invention is described in greater detail in the following using anexemplary embodiment.

FIG. 1 a illustrates the profile of the shaped body, with the flow goingaround it in the sub-sonic range;

FIG. 1 b illustrates the position of the supersonic range relative to ashaped body that is in an air flow in the transonic range;

FIG. 2 illustrates the alternating effect of impact pressure fronts on aparticle;

FIG. 3 illustrates the arrangement of shaped bodies moving in oppositionto one another;

FIG. 4 is a section through the disintegration apparatus;

FIG. 5 illustrates a side view of the disintegrator along the line A-Ain accordance with FIG. 4;

FIG. 6 is a section of shaped body.

FIG. 1 a illustrates a typically shaped body 1 together with flow lines9 in the subsonic range. The flow lines 9 initially flow in a laminarmanner around the profile of the shaped body 1, whereby, depending onthe profile of the shaped body 1, the laminar flow can tear away in therear area of the shaped body 1 and turbulences 3 can occur.

FIG. 1 b illustrates the speeds in the so-called transonic speed range.Relative to the surface of the shaped body 1, a zone forms in which therelative speed of the flowing air in part attains sound velocity. Theregion is labeled “M_(a)>1” in FIG. 1 b. The region is limited in therear by an impact pressure front 4 with a brief increase in pressure andsubsequent drop in pressure. The point 5 marks the location ofparticular mechanical stress to the surface of the shaped body 1.

FIG. 2 illustrates the effect of the impact pressure fronts 4 on aparticle 30. The particle 30 passes through an impact pressure front 4twice, alternating in a different direction.

FIG. 3 illustrates the arrangement of the shaped bodies 1 relative toone another. For instance, two groups of shaped bodies 1 a and 1 b areillustrated that rotate clockwise or counterclockwise about the axle 14.In the exemplary embodiment, each group contains 16 shaped bodies thatrotate about the axle 14 at a rotational frequency of 500rotations/second. Given a radius of 100 mm, this results in a relativespeed of approx. 315 meters/second, i.e. approx. 95% of sound velocity.The sequence of the impact pressure fronts 4, without taking intoconsideration the opposing group, is 8 kHz. The particle path 8 in thedisintegration space 29 is illustrated schematically in FIG. 3.

FIG. 4 illustrates a section of an inventive disintegrator. The shapedbodies 1 of the first group 1 a are affixed to the disk A 15. Two groupsper direction of rotation are used in the exemplary embodiment. The diskA 15 is itself affixed to the hub A 28 on the axle 25, which is causedto rotate at the necessary minimum speed by a drive motor 32. The axle25 is borne in the housing 20 via the bearing A 26. A shaft seal A 27prevents particles 30 and impurities from exiting the bearing A 26. Thesecond group of shaped bodies 1 b is affixed to the disk B 16. This diskB 16 is securely joined to the disk B 117 and the axle B 21, whereby theaxle B 21 itself is borne in the housing 20 via the bearing B 24. Thesecond group of shaped bodies 1 b is driven by the motor 33 against thedirection of rotation of the motor 32.

The granulate 7 is added via the filling hopper 31 near the center ofthe disintegrator to the filling chamber 18. Here the granulate 7travels into the area of the impact pressure fronts 4 and is pulverizedon the way to the exterior areas.

In the design of the inventive disintegrator it should be noted that thedisks 15 and 16 rotating at great speed and the shaped bodies 1 affixedthereto pull air along with them, and this air is driven outward bycentrifugal forces. While in the disintegration space 29 a continuouschange occurs in the rotational speed and thus the speed of theparticles 30 is decelerated again and again, the centrifugal force forthe two exterior surfaces 38 and 39 of the two disks 15 and 16 remainsunchanged. In particular for the disk B 16, through which passes thefilling hopper 31, the centrifugally accelerated air can lead toundesired suction of the granulate 7 out of the filling hopper 31 at theexternal surface 39 of the disk B 16 and granulate 7 can be conveyeddirectly to the outlet 34, circumventing the effects of the shapedbodies 1. This effect can be corrected when the exterior surface 39 ofthe disk B 16 is relatively well sealed against the housing 20 by asealing ring 35. Another solution for this problem is to arrange scoops19 on the exterior surface 39 of the disk B 16; these then counteractthe centrifugal force using an opposing air flow.

After passing through the disintegrator space 29, the particles areremoved at the outlet 34, as can be seen in FIG. 5.

It has been demonstrated that having the granulate 7 pass through thedisintegrator just one time is adequate in terms of the desiredcomminution and activation. The described apparatus works continuously.As much granulate 7 as can be added to the filling chamber 18 based onthe geometry of the filling hopper 31 becomes fully prepared powder madeof particles 30 at the outlet 34.

FIG. 6 illustrates one particularly advantageous embodiment of theshaped bodies 1. The pointed shape of the outflow surfaces 37 preventsvertices and thus reduces the drive energy required.

Legend

-   1 Shaped body-   2 Tip of shaped body-   3 Turbulences-   4 Impact pressure front-   5 Initial point of impact pressure front-   6 Limit of transonic area-   7 Granulate-   8 Particle path-   9 Flow lines-   10 Interior radius of shaped body path of disk 16-   11 Interior radius of shaped body path of disk 15-   12 Exterior radius of shaped body path of disk 16-   13 Exterior radius of shaped body path of disk 15-   14 Axis of rotation-   15 Disk A-   16 Disk B-   17 Disk B1-   18 Filling chamber-   19 Scoops-   20 Housing-   21 Shaft B-   22 Hub B-   23 Shaft sealing ring B-   24 Bearing B-   25 Shaft A-   26 Bearing A-   27 Shaft sealing ring A-   28 Hub A-   29 Disintegration space-   30 Particle-   31 Filling hopper-   32 Motor A-   33 Motor B-   34 Outlet-   35 Sealing ring-   36 Inlet opening-   37 Outflow surfaces-   38 Exterior surface of disk A-   39 Exterior surface of disk B

1. Method for the disintegration and tribochemical activation inparticular of inorganic materials, characterized in that the startingmaterials are comminuted (disintegrated) to a particle size of less than1 μm by the effect of impact pressure fronts that occur as compressionshocks on profiles are moved transonically, with a pulse duration of 10μs and a repetition rate of greater than 8 kHz.
 2. Method in accordancewith claim 1, characterized in that during the disintegration ofmaterials with a crystalline structure a conglomerate of activated mixedcrystals is produced that has an increased capacity for crystalformation when water is added.
 3. Method in accordance with claim 1,characterized in that the effective duration of said impact pressurefronts (4) lasts until the crystal lattice structure of said particles(30) has been destroyed.
 4. Method in accordance with claim 1,characterized in that said impact pressure fronts occur due to rotatingshaped bodies (1) that have aerodynamically formed profiles and that areaccelerated to the transonic speed range.
 5. Method in accordance withclaim 1, characterized in that said particles are subjected to impactpressure fronts (4) of shaped bodies (1) that are rotating in oppositionto one another.
 6. Method in accordance with claim 1, characterized inthat the disintegration takes place under protective gas.
 7. Apparatusfor disintegration and tribochemical activation of in particularinorganic materials, characterized in that arranged on rotating disks(15, 16) are shaped bodies (1) that have an aerodynamically shapedprofile and that are continuously moved in the transonic speed range andthat produce impact pressure fronts on their off-flow surfaces. 8.Apparatus in accordance with claim 7, characterized in that said impactpressure fronts are produced by shaped bodies (1) that have anaerodynamically shaped profile and that are arranged on disk-shapedrotors (15, 16) that move in opposition to one another in the transonicspeed range.
 9. Apparatus in accordance with claim 7, characterized inthat the rate of repetition of said impact pressure fronts varies andfrequency portions of the rate of repetition of >15 kHz occur in thesupersonic range.
 10. Apparatus in accordance with claim 7,characterized in that the forward front of said shaped bodies (1) isrounded and its off-flow surfaces meet an acute angle.
 11. Apparatus inaccordance with claim 7, characterized in that the section of saidshaped body (1) has a non-critical profile.